The present invention relates to a device for detecting microscopic droplets which detects a jetting condition of droplets jetted from a nozzle that jets microscopic droplets, and an ink-jet recording apparatus using the same.
In an ink-jet recording apparatus which jets microscopic droplets from a nozzle provided on a recording head on a recording medium for image recording, a jetting condition of ink is detected by the detection of an absence/presence of jetting of an ink droplet (hereinafter referred to as a droplet) from each nozzle, or by the detection of a flying speed of the jetted droplet, before the performance of an image recording, however, since the jetted droplet becomes further microscopic by the improvement of image quality in terms of a printing accuracy in the present years, the microscopic droplet not greater than 4 pico-liter must be detected, today.
In the past, in order to detect the jetting condition of the droplet, a detecting section that is composed of a light emitting element and a light receiving element is provided to cross a traveling course of the droplet, and a shadow against the detecting light representing a piece of droplet passing through between the light emitting element and the light receiving element on the optical axis is received by the light receiving element, and then, a change of amount of light caused by the shadow is detected and amplified, and thereby, the presence of the ink-jet from the nozzle is detected, in the case of detecting the presence/absence of the jetting, for example. However, due to the tendency that the droplet becomes more microscopic in the future and the image quality becomes higher, the shadow of the more microscopic droplet in a size of about ten-odd xcexcm must be detected and its faint signal must be amplified, which causes the fear that correct detection will become difficult due to the deterioration of S/N ratio.
For the measure, a laser diode is used for a light source of the light emitting element so that the light amount per unit area becomes large, or a lens is dropped down when an LED is used for the light source so that the detecting area is stopped down as far as possible, and thereby, it is conceivable that the S/N ratio is improved by making the shadow of the droplet caught by the detecting section to be larger relatively, compared to the detecting area. However, since a carriage moves in the scanning direction, an accuracy for stopping the recording head is requested more and more severely so that the droplet jetted from the nozzle of the recording head may pass through on the optical axis between the light emitting element and the light receiving element, in order to stop the recording head accurately. To improve the stopping accuracy, the higher performance of a motor driving servo including the detection of the position is requested, which causes not only the cost increase but also the deterioration of the total detecting accuracy, caused by the malfunction of the detection owing to the shift of the stopping position.
With the foregoing as a background, there has been proposed a technology wherein the area covered by the droplet in the detecting area that is detectable by the light receiving element is made to be larger so that the microscopic droplet can be detected (Patent document 1), by the manner that a jetting interval in detecting the jetting of the droplet is established to be shorter than the jetting interval in operating the normal printing, or by the manner that a jetting amount of the droplet per unit time in detecting the jetting of the droplet is established to be larger than the jetting amount of the droplet per unit time in operating the normal printing.
(Patent document 1) Japanese TOKKAIHEI 11-78051
However, when the droplets are jetted continuously, there is a following problem, which clears that an appropriate detection cannot be conducted. That is, when the droplet pass through the detection area of the light receiving element, though the change of the amount of light received by the light receiving element is detected, there occurs the condition that the amount of light when the droplets are passing through hardly changes in the technology described in the above-mentioned patent document. Due to this, even if the output signal from the light receiving element is amplified, it is difficult to select only the signal of the changed value of the light amount from the noise component, causing a problem of miss detection, being impossible to obtain a detecting signal having better S/N ratio.
Further, since the droplet is detected optically by the light receiving element, it often comes under the influence of disturbance light in the course of the detecting operation, and S/N ratio of the detected signal is declined by this influence, causing a problem of miss detection.
Still further, there is a case that the light amount detected by the light receiving element varies depending on the type of the droplet such as the difference of color of ink. In such a case, there is a fear of miss detection due to the difference of the sensitivity of the light receiving element for each type of the ink, accordingly, it is desired that the sensitivity is easily adjustable.
Accordingly, the first subject of the present invention is to provide a microscopic droplet detecting device and an ink-jet recording apparatus which can perform, with high S/N ratio, the detection of the jetting condition of the droplets from the nozzle, by discriminating clearly the optical detection and non-detection of the droplets jetted from the nozzle.
Further, the second subject of the present invention is to provide a microscopic droplet detecting device and an ink-jet recording apparatus which can perform, with high S/N ratio, the detection of the jetting condition of the droplets from the nozzle without coming under the influence of the environmental noise such as the disturbance light.
Still further, the third subject of the present invention is to provide a microscopic droplet detecting device and an ink-jet recording apparatus which can always detect the droplets with the stable sensitivity, independently of the type of the droplets.
The above-mentioned matters are solved by the following Structures.
Structure 1 is a microscopic droplet detecting device for detecting the passage of droplets jetted from a nozzle, having therein, a droplet detecting section in which a light emitting element and a light receiving element are arranged to cross over a traveling course of the droplet jetted from the nozzle and the plural droplets can exist in the distance in the traveling direction of the droplets within the detecting limit of the detecting light emitted from the light emitting element to the light receiving element, a jet control section for controlling a jetting of a group of the droplets composed of the plural and continuous droplets which are jetted from the nozzle, and a jetting condition detecting section for detecting the jetting condition of the droplets from the nozzle, based on the output signal which is obtained by detecting the droplets group controlled by the jet control section by the droplet detecting section, wherein the jet controlling section provides a suspension period in which the droplet is not jetted between a preceding group of serial droplets and a following group of serial droplets which are measured by the droplet detecting section, and wherein when the suspension period is represented by xcex2, a distance along the traveling direction of the group of serial droplets (hereinafter referred to as the droplets group) within the detecting limit of the droplet detecting section is represented by L (m), and a speed of the droplets for passing through the detecting limit of the droplet detecting section is represented by V (m/sec), the condition expressed by xcex2xe2x89xa7L/V is satisfied.
In Structure 1, by providing the suspension period xcex2 so as to satisfy the above-mentioned condition, the distance between the droplets group having passed through the detecting limit of the droplet detecting section in first and the next droplets group having passed through is greater than distance L representing the distance along the traveling direction of the droplets within the detecting limit of the droplet detecting section, and due to this, even when the droplets groups are jetted continuously from the same nozzle or the different nozzle, a group of serial droplets passes through the detecting limit of the droplet detecting section, one by one, and an output signal from the light receiving element is obtained as a single combined signal, and due to this, the output signal from the light receiving element can discriminate the detecting condition by passing of a serial droplets group from the non-detecting condition of the suspension period clearly, by which a noise component is easily eliminated by a high pass filter, thus, it is possible to obtain the microscopic droplet detecting device that can take out only the detecting signal having a better S/N ratio.
Structure 2 is the microscopic droplet detecting device described in Structure 1, wherein xcex2 satisfies the condition 5 m secxe2x89xa7xcex2.
In Structure 2, since the suspension period xcex2 satisfies the above-mentioned condition, the influence caused by the disturbance light existing in the vicinity of 200 Hz or by noise from the power supply can be reduced, and it is possible to conduct the detection having a better S/N ratio, accordingly.
Structure 3 is a microscopic droplet detecting device described in Structure 1, wherein when xcex1n represents the time obtained by dividing the distance between a center of a top droplet and a center of a last droplet which compose a droplets group with an average speed of the droplet, xcex1n satisfies the following formula.
5 m secxe2x89xa7xcex1nxe2x89xa70.5L/V 
In Structure 3, when xcex1n is in the aforementioned limit, an influence of a noise is less and a sufficient signal output can be obtained.
Structure 4 is the microscopic droplet detecting device described in Structure 1, wherein the jet control section can change the number of the droplets which compose the droplets group.
Structure 4 can adjust the sensitivity of the light receiving element, when the droplets group passes through the detecting limit of the droplet detecting section, and can also keep up easily with a further down sizing of the droplet that is expected in future.
Structure 5 is a microscopic droplet detecting device for detecting the passage of droplets jetted from a nozzle, having therein, a droplet detecting section in which a light emitting element and a light receiving element are arranged to cross over a traveling course of the droplet jetted from the nozzle and the plural droplets can exist in the distance in the traveling direction of the droplets within the detecting limit of the detecting light emitted from the light emitting element to the light-receiving element, a jet control section for controlling a jetting of the droplets group composed of the plural and continuous droplets which are jetted from the nozzle, and a jetting condition detecting section for detecting the jetting condition of the droplets from the nozzle, based on the output signal which is obtained by detecting the droplets group controlled by the jet control section by the droplet detecting section, wherein, wherein when xcex1n represents the time obtained by dividing the distance between a center of a top droplet and a center of a last droplet which compose a droplet group with an average speed of the droplet, xcex1n satisfies the following formula.
5 m secxe2x89xa7xcex1nxe2x89xa70.5L/V 
Structure 5 can make the microscopic droplet detecting device which is hardly influenced by a disturbance light existing in the vicinity of 200 Hz and by noise from power supply and is able to obtain the sufficient signal output in the light receiving element.
Structure 6 is the microscopic droplet detecting device described in Structure 5, wherein the above-mentioned jet control section can change the number of the droplets which compose the droplets group.
Structure 6 can adjust the sensitivity of the light receiving element, when the droplets group passes through the detecting limit of the droplet detecting section, and can also keep up easily with a further down sizing of the droplet that is expected in future.
Structure 7 is the microscopic droplet detecting device for detecting the passage of droplets jetted from a nozzle, having therein, a droplet detecting section in which a light emitting element and a light receiving element are arranged to cross over a traveling course of the droplet jetted from the nozzle and the plural droplets can exist in the distance in the traveling direction of the droplets within the detecting limit of the detecting light emitted from the light emitting element to the light receiving element, a jet control section for controlling a jetting of the droplets group composed of the plural and continuous droplets which are jetted from the nozzle, and a jetting condition detecting section for detecting the jetting condition of the droplets from the nozzle, based on the output signal which is obtained by detecting the droplets group controlled by the jet control section by the droplet detecting section, wherein the jet control section can change the number of the droplets which compose the droplets group.
Structure 7 can adjust the sensitivity of the light receiving element, when the droplets group passes through the detecting limit of the droplet detecting section, and can also keep up easily with a further down sizing of the droplet that is expected in future.
Structure 8 is the microscopic droplet detecting device described in Structure 4, wherein the above-mentioned jet controlling section changes the number of the droplets which compose a droplets group, in accordance with the level of the output signal that is detected by the droplet detecting device.
Structure 8 can establish the more appropriate number of the droplets.
Structure 9 is the microscopic droplet detecting device described in Structure 4, 6 or 7, wherein the jet controlling means changes the number of the droplets which compose a droplets group, in accordance with the type of the microscopic droplets.
Structure 9 can obtain the stably detected output independently of the type of the microscopic droplet so that the invention can always conduct the correct detecting operation.
Structure 10 is the microscopic droplet detecting device described in Structure 9 having therein a discriminating section for discriminating the type of the microscopic droplet jetted from the nozzle, wherein the above-mentioned jet control section changes the number of the droplets which compose a droplets group, in accordance with the type of the microscopic droplet that is discriminated by the discriminating section.
Structure 10 can automatically control the change of the number of the droplets, in accordance with the type of the microscopic droplet.
Structure 11 is the microscopic droplet detecting device described in Structure 9 having therein a table in which the relationship between the type of the microscopic droplet and the number of the droplets composing a droplets group according to the type is memorized in advance, wherein the above-mentioned jet controlling section changes the number of the droplets which compose a droplets group, in accordance with the table.
Structure 11 can quickly determine the proper number of the droplets, in accordance with the type of the microscopic droplets.
Structure 12 is the microscopic droplet detecting device described in Structure 9, wherein the type of the above-mentioned microscopic droplets is either one of a color, density, viscosity, temperature characteristics, and composition of the microscopic droplet.
Structure 12 can control the proper number of the droplets from the various view points of the microscopic droplet to change the number so that the more correct detecting operation can be conducted.
Structure 13 is an ink-jet recording apparatus that conducts the recording on a recording medium by jetting microscopic droplets of ink from a nozzle of a recording head, having therein, a droplet detecting section in which a light emitting element and a light receiving element are arranged to cross over a traveling course of the droplet jetted from the nozzle and the plural droplets can exist in the distance in the traveling direction of the droplets within the detecting limit of the detecting light emitted from the light emitting element to the light receiving element, a jet control section for controlling a jetting of the droplets group composed of the plural and continuous droplets which are jetted from the nozzle, and a jetting condition detecting section for detecting the jetting condition of the droplets from the nozzle, based on the output signal which is obtained by detecting the droplets group controlled by the jet control section by the droplet detecting section, wherein the jet controlling section provides a suspension period in which the droplet is not jetted between a preceding group and a following group which are measured by the droplet detecting section, and wherein when the suspension period is represented by xcex2, a distance along the traveling direction of the droplets group within the detecting limit of the droplet detecting section is represented by L (m), and a speed of the droplets for passing through the detecting limit of the droplet detecting section is represented by V (m/sec),
the condition expressed by xcex2xe2x89xa7L/V is satisfied.
In Structure 13, by providing the suspension period xcex2 so as to satisfy the above-mentioned condition, the distance between the droplets group having passed through the detecting limit of the droplet detecting section in first and the next droplets group having passed through is greater than distance L representing the distance along the traveling direction of the droplets within the detecting limit of the droplet detecting section, and due to this, even when the droplets groups are jetted continuously from the same nozzle or the different nozzle, a droplets group passes through the detecting limit of the droplet detecting section, one by one, and an output signal from the light receiving element is obtained as a single combined signal, and due to this, the output signal from the light receiving element can discriminate the detecting condition by passing of a droplets group from the non-detecting condition of the suspension period clearly, by which a noise component is easily eliminated by a high pass filter, thus, it is possible to obtain the ink-jet recording apparatus that can take out only the detecting signal having a better S/N ratio.
Structure 14 is the ink-jet recording apparatus described in Structure 1, wherein xcex2 satisfies the condition 5 m secxe2x89xa7xcex2.
In Structure 14, since the suspension period xcex2 satisfies the above-mentioned condition, the influence caused by the disturbance light existing in the vicinity of 200 Hz or by noise from the power supply can be reduced, and it is possible to conduct the detection having a better S/N ratio, accordingly.
Structure 15 is the ink-jet recording apparatus described in Structure 13, wherein when xcex1n represents the time obtained by dividing the distance between a center of a top droplet and a center of a last droplet which compose a droplets group with an average speed of the droplet, xcex1n satisfies the following formula.
5 m secxe2x89xa7xcex1nxe2x89xa70.5L/V 
In Structure 15, when xcex1n is in the aforementioned limit, an influence of a noise is less and a sufficient signal output can be obtained.
Structure 16 is the ink-jet recording apparatus described in Structure 13, wherein the jet control section can change the number of the droplets which compose the droplets group.
Structure 16 can adjust the sensitivity of the light receiving element, when the droplets group passes through the detecting limit of the droplet detecting section, and can also keep up easily with a further down sizing of the droplet that is expected in future.
Structure 17 is the ink-jet recording apparatus for detecting the passage of droplets jetted from a nozzle, having therein, a droplet detecting section in which a light emitting element and a light receiving element are arranged to cross over a traveling course of the droplet jetted from the nozzle and the plural droplets can exist in the distance in the traveling direction of the droplets within the detecting limit of the detecting light emitted from the light emitting element to the light receiving element, a jet control section for controlling a jetting of the droplets group composed of the plural and continuous droplets which are jetted from the nozzle, and a jetting condition detecting section for detecting the jetting condition of the droplets from the nozzle, based on the output signal which is obtained by detecting the droplets group controlled by the jet control section by the droplet detecting section, wherein, wherein when xcex1n represents the time obtained by dividing the distance between a center of a top droplet and a center of a last droplet which compose a droplets group with an average speed of the droplet, an satisfies the following formula.
5 m secxe2x89xa7xcex1nxe2x89xa70.5L/V 
Structure 17 can make the ink-jet recording apparatus which is hardly influenced by a disturbance light existing in the vicinity of 200 Hz and by noise from power supply and is able to obtain the sufficient signal output in the light receiving element.
Structure 18 is the ink-jet recording apparatus described in Structure 17, wherein the above-mentioned jet control section can change the number of the droplets which compose the droplets group.
Structure 18 can adjust the sensitivity of the light receiving element, when the droplets group passes through the detecting limit of the droplet detecting section, and can also keep up easily with a further down sizing of the droplet that is expected in future.
Structure 19 is the ink-jet recording apparatus for detecting the passage of droplets jetted from a nozzle, having therein, a droplet detecting section in which a light emitting element and a light receiving element are arranged to cross over a traveling course of the droplet jetted from the nozzle and the plural droplets can exist in the distance in the traveling direction of the droplets within the detecting limit of the detecting light emitted from the light emitting element to the light receiving element, a jet control section for controlling a jetting of the droplets group composed of the plural and continuous droplets which are jetted from the nozzle, and a jetting condition detecting section for detecting the jetting condition of the droplets from the nozzle, based on the output signal which is obtained by detecting the droplets group controlled by the jet control section by the droplet detecting section, wherein the jet control section can change the number of the droplets which compose the droplets group.
Structure 19 can adjust the sensitivity of the light receiving element of the ink-jet recording apparatus, when the droplets group passes through the detecting limit of the droplet detecting section, and can also keep up easily with a further down sizing of the droplet that is expected in future.
Structure 20 is the ink-jet recording apparatus described in Structure 16, wherein the above-mentioned jet controlling section changes the number of the droplets which compose a droplets group, in accordance with the level of the output signal that is detected by the droplet detecting device.
Structure 20 can establish the more appropriate number of the droplets.
Structure 21 is the ink-jet recording apparatus described in Structure 16, wherein the jet controlling means changes the number of the droplets which compose a droplets group, in accordance with the type of the microscopic droplets.
Structure 21 can obtain the stably detected output independently of the type of the microscopic droplet so that the invention can always conduct the correct detecting operation.
Structure 22 is the ink-jet recording apparatus described in Structure 21 having therein a discriminating section for discriminating the type of the microscopic droplet jetted from the nozzle, wherein the above-mentioned jet control section changes the number of the droplets which compose a droplets group, in accordance with the type of the microscopic droplet that is discriminated by the discriminating section.
Structure 22 can automatically control the change of the number of the droplets, in accordance with the type of the microscopic droplet.
Structure 23 is the ink-jet recording apparatus described in Structure 21 having therein, a table in which the relationship between the type of the microscopic droplet and the number of the droplets composing the droplets group according to the type is memorized in advance, wherein the above-mentioned jet controlling section changes the number of the droplets which compose the droplets group, in accordance with the table.
Structure 23 can quickly determine the proper number of the droplets, in accordance with the type of the microscopic droplets.
Structure 24 is the ink-jet recording apparatus described in Structure 21, wherein the type of the above-mentioned microscopic droplets is either one of a color, density, viscosity, temperature characteristics, and composition of the microscopic droplet.
Structure 24 can control the proper number of the droplets from the various view points of the microscopic droplet to change the number so that the more correct detecting operation can be conducted.